[The medulloblastoma]

Medulloblastoma is a cerebellar small cell tumor, whose ancestor cell has not been yet identified in the human normal embriology: its exact origin is, in fact, still unknown. Nevertheless, one of the most acceptable possibilities facing the origin of the tumor is the remaining rests of cerebellar outer granular sheet. It is a predominantly infantile tumor, less frequent in young adults, and World Health Organization (WHO) classification has assignated grade IV of malignancy. In this publication of the WHO, medulloblastomas have been subclassified into: classic, desmoplastic, medulloblastomas with extensive nodularity and advanced neuronal differentiation and large cell medulloblastomas. Real differences dealing with survival and prognosis amidst these subvarieties have been noted in extensive series.

The most frequently genetic alteration is the presence of isochromosome 17q in most of 50% of the cases.